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The Effect of Grinding on the True Metabolizable Energy Value of Hull-Less Barley1
The Effect of Grinding on the True Metabolizable Energy Value of Hull-Less Barley1 I. R. SIBBALD
Animal Research Centre, Agriculture Canada, Ottawa, Ontario, Canada K1A 0C6
1982 Poultry Science 61:2509-2511 INTRODUCTION The true metabolizable energy (TME) value of normal barley (i.e., barley with a hull) varies inversely with the crude fiber content (Sibbald and Price, 1976). Consequently, hull-less barley might be expected to contain more TME than normal barley. However, the TME values of samples of six hull-less barleys ranged from 14.55 to 15.22, with a mean of 15.00, MJ/kg of dry matter, which was within the range of 19 normal feed barleys (Sibbald, 1977). Recently, samples of an additional nine hull-less barleys yielded TME values ranging from 13.27 to 15.43, with a mean of 14.23 MJ/kg DM (Sibbald, unpublished). Excreta collected during the latter work contained white fragments that gave a positive reaction to an iodine (starch) test. The digestibility of the starch might have been increased by finer grinding of the barley prior to feeding. The purpose of the experiment being reported was to measure the effect of grinding on the TME value of hull-less barley.
set of subsamples was ground to pass a 20-mesh screen. The coarsely ground subsamples were subjected to a sieve analysis (Wilcox et al, 1970). A similar analysis was attempted on the fine-ground material but was not successful because of the difficulty of quantitative recovery from the sieves. Following the sieve analyses, the fractions of the subsamples were recombined to form two lots of 10 subsamples; these were then assayed for TME (Sibbald, 1976) using a 48-hr excreta collection period. Six adult, Single Comb White Leghorn cockerels were used individually to assay each subsample. The barleys and excreta samples were assayed for total nitrogen (AOAC, 1980), and the TME values were corrected to zero nitrogen balance (TME n ) by assuming that body nitrogen yields excretory products containing 36.51 kj/g of nitrogen (Titus et al., 1959). The correction was applied to the excreta energy outputs of both the fed and unfed birds.
MATERIALS AND METHODS
RESULTS AND DISCUSSION
Ten 400-g samples of hull-less barley, each representing a different cultivar, were each divided into two subsamples. The first set of subsamples was coarsely ground by repeatedly passing through a Wiley mill from which the screen was removed. Each sample was passed through the mill five to nine times. The second
The experimental results are summarized in Table 1. There were distinct differences in particle size between the two grinds, but among cultivars within grinds, differences were comparatively small. The mean TME values spanned a narrow range (14.39 to 15.86 MJ/kg DM) comparable to those observed in earlier assays. The finely ground subsamples had a slightly (P<.05) lower mean TME value than the coarsely ground subsamples (15.06 vs. 15.30 MJ/kg DM). Neither differences among the
'Contribution Number 1087, Animal Research Centre.
2509
Downloaded from http://ps.oxfordjournals.org/ at University of Georgia on June 27, 2015
(Received for publication May 18, 1982) ABSTRACT The cultivars of hull-less barley, each coarsely and finely ground, were assayed for true metabolizable energy (TME) and TME corrected to zero nitrogen balance (TMEn). The finely ground barleys contained less TME (P<.05) than the coarsely ground barleys, but differences among cultivars were not significant (P<.05). The TMEn values were consistently smaller than the TME values; the correction reduced the error mean square in the analysis of varience by 40%. There was a significant interaction between cultivars and grinds in the TMEn data (P<.05), but the differences were small. The TME values of hull-less barley were similar to those of normal barleys with hulls and were not increased by fine grinding. (Key words: true metabolizable energy, grinding, hull-less barley)
SIBBALD
2510
TABLE 1. Comparison of the TMEan d TMEn values of two grinds of hull-less barley Coarse grind 2
Fine grin db
Cultivar sample
Particle size
TMEC
TME n c
1 2 3 4 5 6 7 8 9 10
1129-2390 870-2215 1114-2416 847-2138 886-2168 960-2288 1106-2447 1181-2423 1207-2508 1130-2431
14.92 15.10 14.87 15.86 15.53 15.68 15.38 14.96 15.45 15.27 15.30
TMEC
TMEC
14.42 14.58 14.22 15.30 14.99 14.93 15.01 14.71 15.08 14.81
14.96 15.06 15.31 15.43 15.15 14.90 15.34 15.16 14.90 14.39
14.50 14.59 14.74 14.68 14.68 14.37 14.84 14.61 14.43 13.97
14.80
15.06
14.54
(MJ/kg)
Particle size is given as the range, in microns, within which 68% of the particles fall (see Wilcox et al., 1970). All fine ground material was less than 841 ju in diameter, more than 95% was less than 500 n, and approximately 20% was less than 250 JI. The standard errors appropriate to individual means are TME .252 and TMEn .196.
cultivars nor interactions (grinds X cultivars) were significant (P>.05). The TME n values were consistently smaller than the TME values and, in the analysis of variance, the error mean square was reduced by 40%. The statistical analysis was, therefore, more sensitive and the difference in TME n values between the coarse and fine grinds (14.80 vs. 14.54 MJ/kg DM) was highly significant (P<.01). However, the interaction cultivars X grinds was also significant (P<.05); the TME n values of cultivars 1 to 3 were slightly greater and the values for cultivars 4 to 10 were slightly smaller than the values of their coarsely ground counterparts. The TME values of hull-less oats are substantially greater than those of their normal counterparts (Sibbald and Price, 1977); this is attributed to their lower fiber content. However, the TME and TME n values of the hull-less barleys, assayed in the present experiment, were comparable to the TME values of normal barleys assayed by Sibbald and Price (1976). Presumably, inefficient utilization of some carbohydrate fraction(s) of the hull-less barley compensated for the reduction in fiber content. When excreta samples were stained with iodine no blue color was detected, but this cannot be considered conclusive evidence of the absence of starch because of
the finely divided nature of the excreta and the interference and dominance of other pigments. Overall, fine grinding decreased rather than enhanced energy availability, possibly because of heat damage to protein. The grinding effects were small, inconsistent, and of little practical importance except, perhaps, to emphasize the futility of attempting to increase the energy availability of hullless barley by grinding more finely. The nitrogen correction caused an overall mean reduction of 3.4% in the TME values. Similar reductions in the TME values of wheat and oats were reported by Sibbald and Morse (1983). Of greater importance is the 40% reduction in the error mean square, which is the same as that observed by Sibbald and Morse (1983). Much of the variation in excreta energy output among birds on the same treatment was associated with differences in nitrogen balance and was controlled by the nitrogen correction.
ACKNOWLEDGMENTS The author wishes to thank B. Rossnagel, University of Saskatchewan, and S. O. Fejer, Ottawa Research Station, for supplying the hull-less barleys. Valuable technical support was provided by S. Tobin.
Downloaded from http://ps.oxfordjournals.org/ at University of Georgia on June 27, 2015
Mean
RESEARCH NOTE REFERENCES Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 11th ed. Assoc. Offic. Anal. Chem., Washington, DC. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55: 303-308. Sibbald, I. R., 1977. The true metabolizable energy values of some feedingstuffs. Poultry Sci. 56: 380-382. Sibbald, I. R., and P. M. Morse, 1983. Effects of the nitrogen correction and of feed intake on true metabolizable energy values. Poultry Sci. (In press). Sibbald, I. R., and K. Price, 1976. True metabolizable energy values for poultry of Canadian barleys
2511
measured by bioassay and predicted from physical and chemical data. Can. J. Anim. Sci. 56: 775-782. Sibbald, I. R., and K. Price, 1977. True and apparent metabolizable energy values for poultry of Canadian wheats and oats measured by bioassay and predicted from physical and chemical data. Can. J. Anim. Sci. 57:365-374. Titus, H. W., A. L. Mehring Jr., D. Johnson Jr., L. L. Nesbitt, and T. Tomas, 1959. An evaluation of M.C.F. (Micro-Cel-Fat), a new type of fat product. Poultry Sci. 38:1114-1119. Wilcox, R. A., C. W. Deyoe, and H. B. Pfost, 1970. A method for determining and expressing the size of feed particles by sieving. Poultry Sci. 49:9-13. Downloaded from http://ps.oxfordjournals.org/ at University of Georgia on June 27, 2015
Animal Research Centre, Agriculture Canada, Ottawa, Ontario, Canada K1A 0C6
1982 Poultry Science 61:2509-2511 INTRODUCTION The true metabolizable energy (TME) value of normal barley (i.e., barley with a hull) varies inversely with the crude fiber content (Sibbald and Price, 1976). Consequently, hull-less barley might be expected to contain more TME than normal barley. However, the TME values of samples of six hull-less barleys ranged from 14.55 to 15.22, with a mean of 15.00, MJ/kg of dry matter, which was within the range of 19 normal feed barleys (Sibbald, 1977). Recently, samples of an additional nine hull-less barleys yielded TME values ranging from 13.27 to 15.43, with a mean of 14.23 MJ/kg DM (Sibbald, unpublished). Excreta collected during the latter work contained white fragments that gave a positive reaction to an iodine (starch) test. The digestibility of the starch might have been increased by finer grinding of the barley prior to feeding. The purpose of the experiment being reported was to measure the effect of grinding on the TME value of hull-less barley.
set of subsamples was ground to pass a 20-mesh screen. The coarsely ground subsamples were subjected to a sieve analysis (Wilcox et al, 1970). A similar analysis was attempted on the fine-ground material but was not successful because of the difficulty of quantitative recovery from the sieves. Following the sieve analyses, the fractions of the subsamples were recombined to form two lots of 10 subsamples; these were then assayed for TME (Sibbald, 1976) using a 48-hr excreta collection period. Six adult, Single Comb White Leghorn cockerels were used individually to assay each subsample. The barleys and excreta samples were assayed for total nitrogen (AOAC, 1980), and the TME values were corrected to zero nitrogen balance (TME n ) by assuming that body nitrogen yields excretory products containing 36.51 kj/g of nitrogen (Titus et al., 1959). The correction was applied to the excreta energy outputs of both the fed and unfed birds.
MATERIALS AND METHODS
RESULTS AND DISCUSSION
Ten 400-g samples of hull-less barley, each representing a different cultivar, were each divided into two subsamples. The first set of subsamples was coarsely ground by repeatedly passing through a Wiley mill from which the screen was removed. Each sample was passed through the mill five to nine times. The second
The experimental results are summarized in Table 1. There were distinct differences in particle size between the two grinds, but among cultivars within grinds, differences were comparatively small. The mean TME values spanned a narrow range (14.39 to 15.86 MJ/kg DM) comparable to those observed in earlier assays. The finely ground subsamples had a slightly (P<.05) lower mean TME value than the coarsely ground subsamples (15.06 vs. 15.30 MJ/kg DM). Neither differences among the
'Contribution Number 1087, Animal Research Centre.
2509
Downloaded from http://ps.oxfordjournals.org/ at University of Georgia on June 27, 2015
(Received for publication May 18, 1982) ABSTRACT The cultivars of hull-less barley, each coarsely and finely ground, were assayed for true metabolizable energy (TME) and TME corrected to zero nitrogen balance (TMEn). The finely ground barleys contained less TME (P<.05) than the coarsely ground barleys, but differences among cultivars were not significant (P<.05). The TMEn values were consistently smaller than the TME values; the correction reduced the error mean square in the analysis of varience by 40%. There was a significant interaction between cultivars and grinds in the TMEn data (P<.05), but the differences were small. The TME values of hull-less barley were similar to those of normal barleys with hulls and were not increased by fine grinding. (Key words: true metabolizable energy, grinding, hull-less barley)
SIBBALD
2510
TABLE 1. Comparison of the TMEan d TMEn values of two grinds of hull-less barley Coarse grind 2
Fine grin db
Cultivar sample
Particle size
TMEC
TME n c
1 2 3 4 5 6 7 8 9 10
1129-2390 870-2215 1114-2416 847-2138 886-2168 960-2288 1106-2447 1181-2423 1207-2508 1130-2431
14.92 15.10 14.87 15.86 15.53 15.68 15.38 14.96 15.45 15.27 15.30
TMEC
TMEC
14.42 14.58 14.22 15.30 14.99 14.93 15.01 14.71 15.08 14.81
14.96 15.06 15.31 15.43 15.15 14.90 15.34 15.16 14.90 14.39
14.50 14.59 14.74 14.68 14.68 14.37 14.84 14.61 14.43 13.97
14.80
15.06
14.54
(MJ/kg)
Particle size is given as the range, in microns, within which 68% of the particles fall (see Wilcox et al., 1970). All fine ground material was less than 841 ju in diameter, more than 95% was less than 500 n, and approximately 20% was less than 250 JI. The standard errors appropriate to individual means are TME .252 and TMEn .196.
cultivars nor interactions (grinds X cultivars) were significant (P>.05). The TME n values were consistently smaller than the TME values and, in the analysis of variance, the error mean square was reduced by 40%. The statistical analysis was, therefore, more sensitive and the difference in TME n values between the coarse and fine grinds (14.80 vs. 14.54 MJ/kg DM) was highly significant (P<.01). However, the interaction cultivars X grinds was also significant (P<.05); the TME n values of cultivars 1 to 3 were slightly greater and the values for cultivars 4 to 10 were slightly smaller than the values of their coarsely ground counterparts. The TME values of hull-less oats are substantially greater than those of their normal counterparts (Sibbald and Price, 1977); this is attributed to their lower fiber content. However, the TME and TME n values of the hull-less barleys, assayed in the present experiment, were comparable to the TME values of normal barleys assayed by Sibbald and Price (1976). Presumably, inefficient utilization of some carbohydrate fraction(s) of the hull-less barley compensated for the reduction in fiber content. When excreta samples were stained with iodine no blue color was detected, but this cannot be considered conclusive evidence of the absence of starch because of
the finely divided nature of the excreta and the interference and dominance of other pigments. Overall, fine grinding decreased rather than enhanced energy availability, possibly because of heat damage to protein. The grinding effects were small, inconsistent, and of little practical importance except, perhaps, to emphasize the futility of attempting to increase the energy availability of hullless barley by grinding more finely. The nitrogen correction caused an overall mean reduction of 3.4% in the TME values. Similar reductions in the TME values of wheat and oats were reported by Sibbald and Morse (1983). Of greater importance is the 40% reduction in the error mean square, which is the same as that observed by Sibbald and Morse (1983). Much of the variation in excreta energy output among birds on the same treatment was associated with differences in nitrogen balance and was controlled by the nitrogen correction.
ACKNOWLEDGMENTS The author wishes to thank B. Rossnagel, University of Saskatchewan, and S. O. Fejer, Ottawa Research Station, for supplying the hull-less barleys. Valuable technical support was provided by S. Tobin.
Downloaded from http://ps.oxfordjournals.org/ at University of Georgia on June 27, 2015
Mean
RESEARCH NOTE REFERENCES Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 11th ed. Assoc. Offic. Anal. Chem., Washington, DC. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55: 303-308. Sibbald, I. R., 1977. The true metabolizable energy values of some feedingstuffs. Poultry Sci. 56: 380-382. Sibbald, I. R., and P. M. Morse, 1983. Effects of the nitrogen correction and of feed intake on true metabolizable energy values. Poultry Sci. (In press). Sibbald, I. R., and K. Price, 1976. True metabolizable energy values for poultry of Canadian barleys
2511
measured by bioassay and predicted from physical and chemical data. Can. J. Anim. Sci. 56: 775-782. Sibbald, I. R., and K. Price, 1977. True and apparent metabolizable energy values for poultry of Canadian wheats and oats measured by bioassay and predicted from physical and chemical data. Can. J. Anim. Sci. 57:365-374. Titus, H. W., A. L. Mehring Jr., D. Johnson Jr., L. L. Nesbitt, and T. Tomas, 1959. An evaluation of M.C.F. (Micro-Cel-Fat), a new type of fat product. Poultry Sci. 38:1114-1119. Wilcox, R. A., C. W. Deyoe, and H. B. Pfost, 1970. A method for determining and expressing the size of feed particles by sieving. Poultry Sci. 49:9-13. Downloaded from http://ps.oxfordjournals.org/ at University of Georgia on June 27, 2015